1. Field of the Invention
This invention pertains to devices for holding and constraining heavy loads in place and more particularly to tying down cargo on flat bed trucks or the like.
2. Description of the Prior Art
Cargo that is carried on large flat bed trucks are secured in place or held down by straps, chains, rope and the like and then locked in place by devices known as "load binders". The loads are often very heavy loads such as stacks of lumber, heavy equipment and the like. If the load is not held securely in place, the load will shift or even fall from the truck. Obviously, when a large load slides off a truck bed, the results can be and often are disastrous. Not only is the load damaged or destroyed, time delays occur as the load is reloaded, but accidents and even deaths have resulted from loads being lost.
The most common type of load binder employed is a mechanical binder having a mechanical clamp mechanism and secured in holding or locking condition by a large handle that operates as a lever to give the operator the necessary mechanical advantage to close the load binding connection. The handle is part of the mechanism itself and stays in position when the connection or lock is completed.
Loads are tied down under quite a bit of tension to ensure that loads cannot shift or that parts of the load, such as a board of lumber, cannot work free from the overall load. Hence, when the load binder is released, care must be exercised to prevent the handle from flying loose too fast and causing injury to the operator or others nearby. In fact, the initial tension applied to the load at the time of tie-down may well be increased by the time the load binder is released. This is because the load could have shifted slightly during transport to put more pressure against the strap, rope, chain, etc. than when the load was originally tied down. In summary, such prior art devices have long been in use but take their toll in injuries every year. They are considered to be very hazardous devices by the operators.
Attempts have been made in the prior art to avoid the traditional type of device just described by employing hydraulic or pneumatic arrangements. Such efforts are exemplified by the device shown in U.S. Pat. No. 2,773,700, Lasswell, issued Dec. 11, 1956. The Lasswell device includes an hydraulic cylinder permanently bolted to the underside of the truck bed. The system requires an hydraulic pump, four-way valving, a pressure switch, a solenoid and a requirement for electrical current to three different mechanisms of this device. In short, the Lasswell is no simple substitute for the traditional load binder. Similar devices are shown in U.S. Pat. No. 3,395,932, Meyers, issued Aug. 6, 1968 and Swiss Pat. No. 7,713,057, Laxo Mekan AB, issued June 1979.
U.S. Pat. No. 3,998,167, Van Gompel, issued Dec. 21, 1976, shows a device that has to be cut free to be released. As noted in the above description, load tie-down puts the tying down parts under a great deal of tension. Cutting the rope or cable to cause release would appear to be a dangerous practice. Moreover, the device could not be used practically with chains, the most common tie-down medium of all.
U.S. Pat. No. 2,249,078, Fox, issued July 15, 1941, shows a rather cumbersome clevis and trunion mechanism operating with an extending rod and which can only be operated in the upright position. It is doubtful that such a device could be used reliably in the rugged conditions that exist for load binders.
U.S. Pat. No. 4,004,777, Despas, issued Jan. 25, 1977, shows an hydraulic tensioning device. The number of parts are exceedingly large and complex. A practical hydraulic device for a load binder application (the Despas device is for tensioning a line on a sailboat) must be simple and rugged and reliable. No constant surveillance of the device is possible in such an application.
U.S. Pat. No. 2,620,160, Ray, issued Oct. 6, 1959, shows a device for hoisting hooks and is not operable except in the vertical position. It does not have a separate mechanical lock and has to use an auxiliary or separate non-self-contained pump.
U.S. Pat. No. 2,907,600, Lowrey, issued Dec. 2, 1952, is of similar design to Ray.
U.S. Pat. No. 3,150,859, Payne, issued Sept. 29, 1964 shows a device that uses a pump which is not a part of the device. It has no mechanical locking part and is designed for the purpose of working on the tracks of a track vehicle. It is generally unsuitable for a load binding application.
U.S. Pat. No. 3,298,663, Hextell, issued Jan. 17, 1967, shows yet another device in which the pump is not integral, a basic requirement for a universal hydraulic load binder. The device does not use a mechanical lock, it uses a 4-way valve. The dog-leg mechanism in Hextell would not appear to be appropriate for a load binder.
U.S. Pat. No. 3,662,994, Jones, issued May 16, 1972, shows an apparatus to push apart or pull two rigid members together. It is not equipped to tighten chain. The device uses an external source for fluid. It has no mechanical locking device and it uses Z-shaped jaws, which are unsuitable on a load binder.
U.S. Pat. No. 2,383,061, Johnson, issued Aug. 21, 1945, uses a pump external to the device and is generally a jack attachment, not a device for applying tension. There is no mechanical locking device provided.
U.S. Pat. No. 4,036,476, Douce et al, issued July 19, 1977, is a different type of mechanism altogether from applicant's device in that it employs a winch permanently located at a fixed location on a truck bed. The device requires a source for fluid or for drawing a vacuum.
U.S. Pat. No. 3,891,187, Bearden, Jr., issued June 24, 1975, shows a device employing a double-acting cylinder and dependent on an external power source. The device employs a 4-way valve and has no mechanical locking device.
Hence, in summary of the known prior art, hydraulic devices have been employed for a myriad of applications, but few attempts have been made to make them suitable for a load binding application. The one or two attempts that have been made to make an hydraulic load binder have been mechanisms that are not self-contained, but which use complicated valving, external fluid sources, external power sources, are permanently affixed to the truck bed and are generally unsuited as a safe and easy-to-use self-contained substitute for the conventional and traditional universal load binder described initially.
Therefore, it is a feature of the present invention to provide an improved hydraulic load binder of simple and self-contained design that can be employed in a universal application.
It is another feature of the present invention to provide an improved hydraulic load binder that is readily operated by an operator at any attitude and which does not employ a permanently attached handle that is only operable under tension potentially hazardous to the operator.